Poster: Regulation of gene expression
Abs #
763: Sugar and gibberellin signals differentially mudulate tissue-dependent promoter activity in germinating cereal grains
During germination of cereal grains, expression of α-amylase genes is differentially regulated by sugar and phytohormone gibberellic acid (GA) signals in embryos and aleurone layers of endosperms. To study the mechanisms of differential sugar and GA regulation, promoters of three α-amylase genes, which are differentially expressed in embryos and aleurone layers, were isolated and fused with a reporter gene. These promoters contain various cis-acting elements known to be regulated by sugar and GA signals. Regulation of the promoter activity by sugar and GA was studied by transient expression assays in rice embryos and barley aleurone layers. GA induction overriding sugar suppression of α-amylase promoter activity was observed in barley aleurone layers but not in rice embryos. By contrast, sugar suppression overriding GA induction of α-amylase promoter activity was observed in rice embryos but not in barley aleurone layers. The tissue-dependent differential regulation of α-amylase promoter activity by GA and sugar signals was found to be modulated through GA and sugar response cis-acting elements and their interacting transcription factors. Our study demonstrates that the differential sensitivity of α-amylase promoter to GA and sugar signals in embryos and aleurone layers may provide a mechanism for controlling α-amylase expression for starch degradation and sugar allocation in cereal grains during germination and early stages of seedling growth.
